It seems to be better than the other cassette book out there in terms of coverage. they list pretty much every type of cassette ever made along with approximate release dates. This might help detect bootlegs - if you're buying a tape made in 1994 it shouldn't use a tape not sold till 1997, and so on.
I got the Neowing one because I had an account there already, but the viewer app (required) only lets you zoom up to 200%. If anyone else buys it they might want to try Fujisan and see if it's better.